Since the question of how to convert various Minolta MC/MD lenses to Canon EF mount comes up regularly, I thought I would post a bit about what I have done recently.

Some months ago while browsing for info on Minolta lenses, I came across a post with a different method for conversion. It required some minor machine work. But, my company happens to have a large machine shop so I could trade favors with a machinist friend. I am a computer server/network administrator/manager, not a machinist.

This link shows the basic steps on how to machine an M42 adapter to fit over a Minolta MC/MD mount. That gave me some ideas on how I could improve on it.

Note, this conversion can be done with ANY Minolta MC/MD lens. Minolta varied the details on just about every lens, but there were several designs with variations.

- Start with an M42 to EOS adapter.
- The machinist uses a lathe to cut off the flange plus another .5mm.
- The inside of the adapter is cut to match the Minolta mount. The fit should be tight and even at the bottom.
- Remove the Minolta mount from lens and remove about .010" from the edge of the Minolta mount that will mate with the Canon camera mount.
- Machine off the "ears" of the Minolta mount so they are even.
- Create cut outs in the M42 adapter for the Minolta screw holes so you can still disassemble the lens if needed. I use the small sanding drum on a Dremel.
- When the M42 mount is fit over the Minolta mount, the center of the Minolta mount may protrude, I sand it off level.
- Glue the machined M42 adapter to the Minolta adapter with the correct orientation. I use 3 small drops of Super Glue.
- Cut a small notch for the camera lens locking pin. I use the Dremel with a cutter, not a drill. Be sure to make the sides vertical or the lens might rotate.

Now it is done. There is no sanding or drilling holes in the adapter, big pluses for me!

Infinity focus should be close, but I usually have to adjust it using the lens' adjustment mechanism.

For someone that likes to do DIY projects, this is not hard at all. But, unless there are interesting lenses to convert there is no point.

The 58mm and 85mm are discussed elsewhere in the forum.

My very brief test shots with the 24/2.8 and 28/2 show them to be excellent so far with good coverage into the corners but I need to do some real world shots. Both have floating elements. I particularly like the 28/2.

Some possible other interesting wide angles are the 20/21mm, 17mm, 16mm fisheye and 24mm VFC. Unfortunately you have to irreversibly modify the lens before you can put it on your camera and evaluate it's quality.

So, this is just another option for people that may want to convert Minolta manual focus lenses.

Nicely done. Presumably you still need to machine down the rear retainer ring where necessary, to clear the mirror for infinity focus? Not that this is an issue with all the Minolta lenses, but certainly is with some (35 1.8, 58 1.2 are the ones i've done so far that have this issue).
-Ed

Ed, my directions were intended to be generic. Any lens that has a mirror clearance problem will still have it when converted by this method. The mirror on my 5D is shaved and the rear element retainer on the 58/1.2 was filed down. Standard procedure unfortunately.

Thanks for the reply, understandable re: rear element retainer ring. Fortunately on the 58 1.2, I think that can be turned down far enough that you can still get to infinity w/o mirror clearance issues on an unshaved full-frame mirror. I have a 58 1.2 that I adapted with a mount from Pete Ganzel. With the lens racked to the infinity stop, it will hit the mirror, but infinity focus is actually past infinity on the lens (I could shim it some more to make it perfect if need be), so when focusing on infinity (a little before where it is on the lens barrel), it will not hit mirror on my 1V.

On the first 35 1.8 I converted, I haven't turned down the rear ring quite enough yet to get it to infinity w/o hitting the mirror, we'll see if it's possible- it might not be. I removed the screw which is the stop for the helicoid that determines infinity (and close-focus limit). Doing so allows it to focus past infinity, which is fine since I still could stand to take a little more off the mount, so even with it all the way to the end (past infinity) it's only getting to about 30ft focus distance currently. On the close-focus end, it will now focus down to about 5-6 inches, near-macro. I haven't tested to see exactly what the ratio is but I bet it's at least 1:3 or 1:4. (normal min focus distance is 1ft, which is admirably short).

It should be easy to adjust infinity focus on the 35/1.8. I don't have the lens but it should be very similar to others, I am going on memory.

When you say you have removed the screw for infinity, that does not sound like the normal way to do it. Sorry if you already know all this, but it may help others.

Remove the front name plate - it unscrews on the filter threads. Underneath there should be three screws that hold the filter assembly. Remove those screws and the filter assembly and there should be three more screws that lock the helicoil.

Focus the lens to infinity. Loosen the three screws about 1 turn. Rotate the barrel with the focus markings to something less than infinity, your best guess on what you can currently focus to - say the 15' mark. Tighten the 3 screws. Now you have more focus travel. Test for infinity. Repeat until you get it right.

The only hard thing is removing the name plate. Sometimes that can be very hard when they have no notches. If you don't have the correct tool, you can sometimes find a drinking glass with the right diameter and use some rubbery shelf liner to create friction.

rgallie wrote:
Since the question of how to convert various Minolta MC/MD lenses to Canon EF mount comes up regularly, I thought I would post a bit about what I have done recently.

Some months ago while browsing for info on Minolta lenses, I came across a post with a different method for conversion. It required some minor machine work. But, my company happens to have a large machine shop so I could trade favors with a machinist friend. I am a computer server/network administrator/manager, not a machinist.

This link shows the basic steps on how to machine an M42 adapter to fit over a Minolta MC/MD mount. That gave me some ideas on how I could improve on it.

Note, this conversion can be done with ANY Minolta MC/MD lens. Minolta varied the details on just about every lens, but there were several designs with variations.

- Start with an M42 to EOS adapter.
- The machinist uses a lathe to cut off the flange plus another .5mm.
- The inside of the adapter is cut to match the Minolta mount. The fit should be tight and even at the bottom.
- Remove the Minolta mount from lens and remove about .010" from the edge of the Minolta mount that will mate with the Canon camera mount.
- Machine off the "ears" of the Minolta mount so they are even.
- Create cut outs in the M42 adapter for the Minolta screw holes so you can still disassemble the lens if needed. I use the small sanding drum on a Dremel.
- When the M42 mount is fit over the Minolta mount, the center of the Minolta mount may protrude, I sand it off level.
- Glue the machined M42 adapter to the Minolta adapter with the correct orientation. I use 3 small drops of Super Glue.
- Cut a small notch for the camera lens locking pin. I use the Dremel with a cutter, not a drill. Be sure to make the sides vertical or the lens might rotate.

Now it is done. There is no sanding or drilling holes in the adapter, big pluses for me!

Infinity focus should be close, but I usually have to adjust it using the lens' adjustment mechanism.

For someone that likes to do DIY projects, this is not hard at all. But, unless there are interesting lenses to convert there is no point.

The 58mm and 85mm are discussed elsewhere in the forum.

My very brief test shots with the 24/2.8 and 28/2 show them to be excellent so far with good coverage into the corners but I need to do some real world shots. Both have floating elements. I particularly like the 28/2.

Some possible other interesting wide angles are the 20/21mm, 17mm, 16mm fisheye and 24mm VFC. Unfortunately you have to irreversibly modify the lens before you can put it on your camera and evaluate it's quality.

So, this is just another option for people that may want to convert Minolta manual focus lenses.

I would have liked to see some explainitory text on the pics as its not easy to understand whats going on simply from the pics.
As a machinist myself I have to point out some flaws I can see in your conversion process.
The Minolta MC/MD mount registration distance is ~43.5mm, and EF registration distance is 44mm so by gluing or otherwise fixing an M42-EF adapter over the top of a Minolta mounting plate is a sure way to guarentee you wont get infinity focus.
The sure way to get infinity focus without having to go to the very tricky extremes of adjusting the helicoid stops is to remove the Minolta mounting plate, machine at least 0.5mm off the Aluminium aperture dial retaining shim/washer, which sits underneath it, then using the Minolta mounting plate as a drill template, drill and countersink new securing holes in your M42-EF adapter to match those in the lens (four will be sufficient) and then using the original screws, secure the M42-EF adapter straight onto the lenses mounting boss. (You could glue the plate on if you wish but then you wont be able to remove it again so screws are a much better option.)

Alf Beharie wrote:
I would have liked to see some explainitory text on the pics as its not easy to understand whats going on simply from the pics.
As a machinist myself I have to point out some flaws I can see in your conversion process.
The Minolta MC/MD mount registration distance is ~43.5mm, and EF registration distance is 44mm so by gluing or otherwise fixing an M42-EF adapter over the top of a Minolta mounting plate is a sure way to guarentee you wont get infinity focus.
The sure way to get infinity focus without having to go to the very tricky extremes of adjusting the helicoid stops is to remove the Minolta mounting plate, machine at least 0.5mm off the Aluminium aperture dial retaining shim/washer, which sits underneath it, then using the Minolta mounting plate as a drill template, drill and countersink new securing holes in your M42-EF adapter to match those in the lens (four will be sufficient) and then using the original screws, secure the M42-EF adapter straight onto the lenses mounting boss. (You could glue the plate on if you wish but then you wont be able to remove it again so screws are a much better option.)...Show more →

One of the steps above is "The machinist uses a lathe to cut off the flange plus another .5mm.". If you want more photos and text and diagrams, look at the link. I did not invent this method, I adapted the method from the link and took it a few steps further.

There are limits to how far you can adjust infinity focus with the lens's internal adjustment, but it is usually much easier than other methods.